Shark dart electronic circuit

ABSTRACT

AN ELECTRONIC CIRCUIT, INCLUDING A SOURCE OF DC POTENTIAL CONNECTED TO AN ASTABLE MULTIVIBRATOR ENABLING A SERIALLY-CONNECTED SWITCH INTERPOSED IN THE FEEDBACK LOOPS OF A SWITCHING INVERTER, COUPLES AN IMMOBILIZING ELECTROMOTIVE FORCE TO THE INTERIOR OF A MARINE PREDATOR&#39;&#39;S BODY VIA A PATHWAY BETWEEN A BLADE-LIKE ELECTRODE IMBEDDED IN THE PREDATOR&#39;&#39;S BODY, AMBIENT SEAWATER, AND A RETURN ELECTRODE. AN &#34;ON-OFF&#34; DUTY CYCLE CONSERVES THE POTENTIAL SOURCE TO ENSURE A LONGER PERIOD OF ELECTRONARCOSIS.

c. 14, 1971 c, B C 3,625,626

SHARK DART ELECTRONIC CIRCUIT Filed July 2%, 1070 F G 2 VUNTOR.

CLARENCE G. BLANC THOMAS G. KEOUGH ERVIN F. JOHNSTON ATTORNEYS d States Patent Office Patented Dec. 14, 1971 ABSTRACT OF THE DISCLOSURE An electronic circuit, including a source of DC potential connected to an astable multivibrator enabling a serially-connected switch interposed in the feedback loops of a switching inverter, couples an immobilizing electromotive force to the interior of a marine predators body via a pathway between a blade-like electrode imbedded in the predators body, ambient seawater, and a return electrode. An on-off duty cycle conserves the potential source to ensure a longer period of electronarcosis.

STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION Contemporary cattle prod-like electric devices, employed for stunning or keeping marine predators at a distance, have suffered from the two major limitations, those being, that they require a diver to hold them against the surface of the predator, and that they often require high potentials creating an undue hazard to the diver. One approach for avoiding these limitations is disclosed in the pending US. patent application, Ser. No. 855,233, entitled: Electronic Anti-Shark Dart by Clarence S. Johnson and Henry D. Baldridge, filed Sept. 4, 1969. This shark dart uses a plurality of batteries along with an electronic circuit for providing shark immobilizing electrical power at a low level and at a safe distance from the diver. However, the batteries tended to degenerate rapidly when full duty cycle operation was demanded. The present invention is in superior circuit for conserving battery power while reliably providing the immobilizing electrical power.

SUMMARY OF THE INVENTION The present invention is directed to providing a circuit for inducing electronarcosis in a marine predator and includes a source of DC power connected to a switching inverter. An astable multivibrator, having a predetermined switching rate, sequentially completes the switching inverter circuit, via a switching transistor, serially-connected in the inverters feedback loops, to provide a partial dutycycle conserving battery power and prolonging the effective life of the shark dart.

It is the prime object of the invention to provide an electronic circuit for creating an immobilizng electric current in a self-contained shark dart.

Yet another object is to provide an electronic circuit allowing only a partial duty cycle to conserve a limited potential source.

An ultimate object of the instant invention is to provide a compact, reliable, long-life, electronic circuit exposing a diver to minimum hazards when using an electric shark dart.

These and other objects of the invention will become readily apparent from the ensuing description when taken with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional depiction of the invention operatively disposed in a shark dart.

FIG. 2 is a schematic representation of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring, now, to the drawings, the invention improves the operating characteristics of the subject matter of a pending US. patent application, Ser. No. 855,233, entitled: Electric Anti-Shark Dart by Clarence S. Johnson and Henry D. Baldridge, filed Sept. 4, 1969. The application reveals that a state of electronarcosis, or paralysis, in a marine predeator is induced by passing a current through its body via an impaling electricanti-shark dart or projectile 10 separable from a spear gun shaft 10a. The present invention provides a means by which the effectivenss of the electric anti-shark dart is greatly increased by making the most efficient use of the available power source.

The circuit includes an electrode 11 having a bladelike configuration to enable penetration deep within a marine predators body. Forming the butt end of the shark dart, a butt electrode 12 is also formed of a conductive material with its outer surface in electrical communication with the ambient seawater.

Internally stored within the shark darts casing, seriallyconnected batteries 13, preferably being nickel cadmium for long life and recharge-ability, are coupled to an enabling switch 14 carried on the exterior of the dart.

The switch has a pair of convergingly biased contacts 14a and 14b, separated by an insulating divider 14c eX- tending from an insulating cup-shaped cap 14d separating the contacts and sealing them from external seawater. A forceful tug on line 14c removes the divider from between the contacts and th ey spring together to complete a circuit. Precise configuration of the switch is not critical to the invention save only for the fact that its manner of construction must be such as to shut out surrounding seawater preventing premature completion of a circuit, as well as allowing circuit actuation when desired.

Operatively connected to the aforedescribed elements, an electronic circuit 15, having a first terminal 15a connected to contact 14:: and a second terminal 15b connected to the batteries, is provided to create a partial duty immobilizing current through the body of the predator to prolong the life of the batteries and, hence, the effectiveness of the shark dart.

Provision is made within this circuit to transfer a narcosis-inducing signal by including a coupling transformer 16, having output terminals 16a and 16b extending to the blade-shaped electrode at point 11a and the butt electrode at butt screw 12a.

On the primary winding side of the coupling transformer, a switching inverter 20, otherwise known as a DC-AC power oscillator, includes a pair of transistors 21 and 22 arranged in a push-pull relationship. A single rimary winding 23, supplying flux for the coupling transormer, is center-tapped to link batteries 13 through the ollectors of the pair of transistors. Each transistor base connected to a separate feedback loop, resistor 21a nd winding 21b forming separate elements in the feedack loop associated with transistor 21 and resistor 22a nd winding 22b forming separate elements in the feedack loop associated with the transistor 22. Both feedack loops share a common resistor 24 that, with the xception of an element to be discussed below, completes he feedback loops of the switching inverter.

Completion of the switching inverter circuit to enable he generation of a predetermined alternating frequency, .ependent on the magnitudes of components used, occurs /hen a transistor switch 25 conducts to complete the eedback loops of the switching inverter.

Sequential actuation of transistor switch 25 is ensured y including an astable multivibrator 30, coupled to the ase of the transistor switch.

The astable multivibrator contains, as a primary comtonent, a unijunction transistor 31 separated from the me of the transistor switch by a charging capacitor 2. A first resistor 33 is also joined to the base of the ransistor switch and a second resistor 34 is connected cross the emitter and base of the unijunction transistor.

A power supply path from source 13 is set up, initially, hrough a first diode 35 and resistor 33 to actuate transisor switch 25 and to start oscillation in switching inerter 20. After the switching inverter begins oscillating,

second power supply path, through winding 16c and econd diode 37, enables the storing of a firing charge or unijunction transistor 31 on storage capacitor 36 to nsure an astable multivibrator capability.

The electronic cooperation of the aforedescribed circuit tassing an immobilizing signal to a shark, or similar redator, becomes more apparent from the following unctional description of the circuits operation.

When blade electrode 11 is inserted deeply into the ody of a shark and cap 14d is pulled from enabling witch 14, the serially-connected batteries are connected 3 switching inverter 20. Since a perfect balance is not chieved between active and passive components included 1 the two feedback loops associated with transistors 21 nd transistors 22, oscillation starts at a frequency preetermined by the values of the resistive and reactive omponents in each feedback loop.

Although the battery also supplies power to astable iultivibrator 30 through the path including first diode 5, unijunction transistor 31 does not fire, for it requires firing potential more than that provided from battery 3 alone. Winding 16c transfers a signal through second iode 37 and reoccurring additive, half-wave portions f an induced voltage in winding 160 are built up on torage capacitor 36. As the critical firing potential suply voltage is accumulated on capacitor 36, usually within No or three cycles, it is also built up on capacitor 32 ia resistor 34.

The unijunction transistor fires and the potential on 1e emitter of transistor switch 25 drops since the change f voltage caused by the unijunction transistors firing transferred to the base of the transistor switch via barging capacitor 32.

The transistor switch turns off and the switching lverter is turned off. Alternating power ceases to be :d to the electrodes and the accumulated signal on apacitor 32 is drained through the unijunction transistor.

Because enabling switch 14 is still closed during the off portion of the cycle, battery power is once again :d through diode 35 and resistor 33 to accumulate a barge on capacitor 32. When the accumulated charge :aches the firing potential of transistor switch 25, it DI'ldllCtS, ending the off portion and restarting the on ortion of the duty cycle. Upon reactuation of the transis- )r switch, the switching inverter is again enabled and n immobilizing signal is again fed to electrodes 11 and 12. Increasing the magnitude of resistor 33 increases the ofl? time of the switching inverter; increasing the magnitude of resistor 34 increases the on time of the switching inverter; and increasing the magnitude of charging capacitor 32 decreases the switching rate between the on and oif state, but does not affect the duty cycle. Experience has demonstrated that a fifty percent duty cycle, a cycle in which immobilizing alternating currents are fed to a shark fifty percent of the time in intermittent bursts, is sufficient to maintain electronarcosis.

In a representative embodiment of the invention having a fifty percent duty cycle, batteries 13 were two Sonotone 2H120 NiCd batteries and coupling transformer 16 was a number 37134601 having a magnetic core. Transistors 21 and 22 were both 2N2912s and transistor switch 25 was an NPS6520. Unijunction transistor 31 was a 2N4871 and first and second diodes 35 and 37 were 1N400ls. All the resistors had a one-fourth watt rating with resistors 21a and 22a both having a value of 22 ohms, and common transistor 24 having a value of 39 ohms. Resistor 33 had a 15 'kilohm value and resistor 34 had a 4.7 kilohm value. Charging capacitor 32 had a 47 microfarad rating at 6 volts and storage capacitor 36 had a 15 microfarad rating at 20 volts.

With the above enumerated elements, the output signal across electrodes 11 and 12 had a 60 volt peak-to-peak spread at a frequency between 1 to 2 kilohertz. The astable multivibrator switched the l to 2 kilohertz 60 volt peak-to-peak signal at a 1 hertz rate with a 50% duty cycle. Thusly, 15 watts of immobilizing power were fed to the marine predator, in this instance, a large shark, for over twenty minutes, far in excess with the total time period had the switching inverter been actuated of the time.

Coating electronic circuit 15 with a dielectric to encase the elements from the surroundings increased reliability by preventing short circuiting caused by leaks through the shark dart housing.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings, and, it is therefore understood that within the scope of the disclosed inventive concept, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An impaling projectile and circuit for inducing electronarcosis in a marine predator comprising:

a source of DC power;

means connected to the power source for converting same to alternating energy,

switching means interposed in the feedback loops of the converting means;

means for enabling said switching means to create sequential bursts of said alternating energy;

a first and a second electrode means carried by the projectile, the first of which being shaped for insertion in said marine predator, the second of which being electrically in contact with the ambient water; and

means coupling said converting means to both said electrode means, upon said insertion, passing immobilizing said sequential bursts for prolonged periods of time between said first and said second electrode means, through said ambient water and through the body of said marine predator.

2. A circuit according to claim -1 further including:

a switch connecting said power source to said converting means for actuation only upon said insertion.

3. A circuit according to claim 1 further including:

an insulating composition encasing said circuit to render it immune from short circuiting by said ambient water.

4. A circuit according to claim 2 in which said converting means is a push-pull inverter, and said switching means is a transistor serially coupled in said feedback loops.

5. A circuit according to claim 4 in which the enabling 3,362,711 1/ 1968 Larsen et a1. 2312 E means is an astable multivibrator coupled to the base of 3,484,665 12/1969 Mountjoy et a1 317-262 said transistor.

References Cit d ALDRICH F. MEDBERY, Primary Examiner 3 UNITIS-ED STATES PATENTS 5 Us CL 8,84 3/18 2 Sounenburg et a1 436 2,805,607 9/1957 Ryan 273 l06.5 2312 27384, 331112 3,310,754 15/1967 Stewart 331l12 

